To begin, let me confess my ignorance about using speedlights.
I was invited to a wedding reception last night as a guest so I figured I'd bring along my D300 and my new SB-600, which I'd never used in a real world situation. To prepare, I dug out my Thom Hogan and set up a "flash" custom shooting bank per his recommendations. But when i tried to use it (speedlight attached to the camera), I couldn't get the SB-600 to fire.
I was trying to use it in A priority with a 50/1.8 wide open at ISO 800. When that didn't work, I switched to another custom bank, "portrait", and that didn't work either. I got it to work using the "point and shoot" bank but the results were not great.
The light in the hall was very dim.
If any of yu have the patience to tell me what I was doing wrong (so I can correct it for the future even though I rarely use flash) I'd be grateful.
BTW, when i stored the speedlight, the onboard flash worked satisfactorily.